Tubular connection center shoulder seal

ABSTRACT

A metal-to-metal sealing system connecting first and second tubular members includes a first seal configuration on the first tubular member and a second seal configuration on the second tubular member. The first seal configuration includes a first annular groove and a first annular tooth, and the second seal configuration includes a second annular groove and a second annular tooth. The second annular tooth is positioned within the first annular groove with the second annular tooth face engaging the first annular shoulder face to define a first shoulder. The first annular tooth is positioned within the second annular groove with the first annular tooth face engaging the second annular shoulder face to define a second shoulder. Locations of primary sealing contact of surfaces of the members are spaced axially away from the first and second shoulders.

CROSS-REFERENCES

This application claims the benefit if U.S. Provisional Application Ser.No. 61/760,833, filed Feb. 5, 2013, the entirety of which isincorporated herein by reference.

TECHNICAL FIELD

The present application relates to tubular connections of the kindcommonly used in the oil and gas industry that include a center-shoulderseal and, more particularly, to a center-shoulder seal configurationthat separates radial and hoop forces of metal-to-metal contact sealingsurfaces from the center shoulders.

BACKGROUND

The Oil & Gas upstream production industry drills wells of everincreasing depth and complexity to find and produce raw hydrocarbons.The industry routinely uses steel pipe (Oil Country Tubular Goods) toprotect the borehole (casing) and to control the fluids produced therein(tubing). Casing and tubing are made and transported in relatively shortlengths and installed in the borehole one length at a time, each lengthbeing connected to the next. As the search for oil and gas has drivencompanies to drill deeper and more difficult wells, the demands on thecasing and tubing have grown proportionately greater in terms of bothtensile and pressure forces. The developing technology of deviated andhorizontal wells have exacerbated this trend, adding to the casing andtubing requirements a further consideration of increasing torsionalloads.

Two general classes of connectors exist within this field. The mostcommon is the threaded and coupled connector, wherein two pin, or malethreads, which are machined on the ends of two long joints of pipe, arejoined by two box, or female threads, machined on a relatively shortmember, a coupling, with a larger outside diameter than the pipe, andapproximately the same inside diameter. The other class is the integralconnector, wherein the pin member is threaded onto one end of afull-length joint of pipe and the box member is threaded into the secondfull-length joint. The two joints can then be directly joined withoutthe need for an intermediate coupling member. The ends of the pipe bodymay be processed further to facilitate the threading of the connection.

The prior art demonstrates the use of a variety of different thread,shoulder and seal configurations for oil country tubular goods. One typeof shoulder and seal combination used in the prior art is the so-calledcenter shoulder seal configuration. As used herein, a “center shoulderseal” is understood to mean a section of a connection disposed betweenat least two threaded portions, which section exhibits directlycontacting surfaces between the pin and box members, or between the pinand box members and a third component such as an annular sealing sleeve,so that the section provides a seal for preventing the passage of liquidor gas through (across the threads of) the assembled connection.

U.S. Pat. Nos. 5,415,442 and 5,462,315 disclose a center shoulderconfiguration, represented in FIG. 1, in which a total of fivemetal-to-metal seals are created during assembly (make-up) of theconnection: two metal-to-metal seals at the exterior beveled edges ofthe locked double shoulder seal 400 where sealing surfaces 418 and 438are in contact and where sealing surfaces 422 and 442 are in contact;and, three zero clearance surfaces at the interior of the locked doubleshoulder seal 400, one 410 at the wall surface where sealing cylindricalsurfaces contact, another zero clearance surface where the annular facesurface of the pin shoulder 420 contacts the box undercut surface 448,and another zero clearance surface where the face surface of boxshoulder 440 contacts pin undercut surface 428. Thus, center-shoulderseal 400 forms a very close fitting metal-to-metal seal having matingmetal-to-metal sealing surfaces which allow a build-up of stored energywithin the seal upon power tightening of the assembled connection, suchthat upon the application of various loads on the pipe and also theconnection, the seal will continue to perform and maintain sealingengagement. Notably, all of the metal-to-metal seals are formed withinthe axial space 450 between the sets of contacting annular faces of thecenter shoulder, and the metal-to-metal seals at the exterior bevelededges of shoulder seal 400, each of which exhibits radial forces, areeach located immediately adjacent a respective one of the sets ofcontacting annular faces.

U.S. Pat. Nos. 5,765,836 and 6,041,487 disclose a center shoulderconfiguration, represented in FIG. 2, in which a total of at least twoand up to seven metal-to-metal seals are established between the pin andbox members. Three of the seven seals are frustum seals. A first outerfrustum seal 120 is formed by the engagement of pin and boxfrustoconical surfaces at the radially outer side of the center shoulderand a second inner frustum seal 122 is formed between pin and boxfrustoconical surfaces at the radially inner side of the centershoulder. The third frustum seal is a center frustum seal 124 formedbetween intermediated pin and box center frustoconical surfaces. Twoannular shoulder seals are formed. A first inner annular shoulder seal126 a second outer annular shoulder seal 128, each by engaged annularsurfaces of the pin and box members. Two cylindrical seals are alsoformed. A first outer cylindrical seal 130 is formed by the engagementof pin and box outer seal cylindrical surfaces at the radially outerside and a second inner cylindrical seal 132 is formed by the engagementof pin and box seal cylindrical surfaces at the radially inner side.Notably, this arrangement also places each of the metal-to-metal sealsthat are exposed to significant radial and hoop forces (i.e., contactingseals 122 and 120) immediately adjacent a respective one of the sets ofcontacting annular faces (i.e., at annular contacting seals 126 and 128)and likewise within the axial space 150 between the two annular shoulderseals.

In the center shoulder configurations of the foregoing patents, axialloading within the shoulder connections tends to produce the higheststresses proximate the axial locations of annular shoulder contact(e.g., at annular shoulder seals 126 and 128 in FIG. 2, and similarly atthe annular shoulder seals formed in the arrangement of FIG. 1). Thus,highest stresses and material yield or deformation tends to occur withinor near the axial region 450, 150 that, in each case, is defined betweenthe annular shoulders of the connection.

What is needed is a center shoulder connection that provides effectivesealing while avoiding potential issues of radial sealing forces in theregion of the high stress and likely yield area of the center shoulder.

SUMMARY

In one aspect, a metal-to-metal sealing system connecting first andsecond tubular members (e.g., such as first and second oil countrytubulars) includes a first seal configuration on the first tubularmember and a second seal configuration on the second tubular member. Thefirst seal configuration includes a first annular groove and a firstannular tooth, the first annular groove defined by a radially inwardfacing undercut surface, an adjacent first annular shoulder face and anadjacent first radially outward facing surface, the first annular toothdefined by the radially inward facing undercut surface, a first annulartooth face and a second radially outward facing surface. The second sealconfiguration includes a second annular groove and a second annulartooth, the second annular groove defined by a radially outward facingundercut surface, an adjacent second annular shoulder face and anadjacent first radially inward facing surface, the second annular toothdefined by the radially outward facing undercut surface, a secondannular tooth face and a second radially inward facing surface. Thesecond annular tooth is positioned within the first annular groove withthe second annular tooth face engaging the first annular shoulder faceto define a first shoulder. The first annular tooth is positioned withinthe second annular groove with the first annular tooth face engaging thesecond annular shoulder face to define a second shoulder. A location ofprimary sealing contact between the first radially outward facingsurface of the first tubular member and the second radially inwardfacing surface of the second tubular member is spaced axially away fromthe first shoulder; and a location of primary sealing contact betweenthe first radially inward facing surface of the second tubular memberand the second radially outward facing surface of the first tubularmember is axially spaced from the second shoulder.

In one implementation of the system of the preceding paragraph,clearance is provided between the first radially outward facing surfaceand the second radially inward facing surface in the vicinity of thefirst shoulder; and clearance is provided between the first radiallyinward facing surface and the second radially outward facing surface inthe vicinity of the second shoulder.

In one implementation of the system of either of the two precedingparagraphs, the location of primary sealing contact between the firstradially outward facing surface and the second radially inward facingsurface is axially spaced from the first shoulder by between about 25thousandths of an inch and about two inches, and the location of primarysealing contact between the first radially inward facing surface and thesecond radially outward facing surface is axially spaced from the secondshoulder by between about 25 thousandths of an inch and about one inch.

In one implementation of the system of any one of the three precedingparagraphs, a radial spacing between the first radially outward facingsurface and the second radially outward facing surface in a plane of thefirst shoulder is between about 40 and about 500 thousandths of an inch,and a radial spacing between the first radially inward facing surfaceand the second radially inward facing surface in a plane of the secondshoulder is between about 40 and about 500 thousandths of an inch.

In one implementation of the system of any one of the four precedingparagraphs, the radially inward facing undercut surface engages theradially outward facing undercut surface.

In one implementation of the system of any one of the five precedingparagraphs, the location of primary sealing contact between the firstradially outward facing surface and the second radially inward facingsurface is formed by interference between one of: (i) a frustoconicalportion of the first radially outward facing surface and a frustoconicalportion of the second radially inward facing surface; (ii) afrustoconical portion of the first radially outward facing surface and acurvilinear portion of the second radially inward facing surface; (iii)a curvilinear portion of the first radially outward facing surface and afrustoconical portion of the second radially inward facing surface; or(iv) a curvilinear portion of the first radially outward facing surfaceand a curvilinear portion of the second radially inward facing surface.Likewise, the location of primary sealing contact between the firstradially inward facing surface and the second radially outward facingsurface is formed by interference between one of: (i) a frustoconicalportion of the first radially inward facing surface and a frustoconicalportion of the second radially outward facing surface; (ii) afrustoconical portion of the first radially inward facing surface and acurvilinear portion of the second radially outward facing surface; (iii)a curvilinear portion of the first radially inward facing surface and afrustoconical portion of the second radially outward facing surface; or(iv) a curvilinear portion of the first radially inward facing surfaceand a curvilinear portion of the second radially outward facing surface.

In another aspect, a metal-to-metal sealing system connecting first andsecond tubular members includes a first seal configuration on the firsttubular member and a second seal configuration on the second tubularmember. The first seal configuration includes a first annular groove anda first annular tooth, the first annular groove defined by a radiallyinward facing undercut surface, an adjacent first annular shoulder faceand an adjacent first radially outward facing surface, the first annulartooth defined by the radially inward facing undercut surface, a firstannular tooth face and a second radially outward facing surface. Thesecond seal configuration includes a second annular groove and a secondannular tooth, the second annular groove defined by a radially outwardfacing undercut surface, an adjacent second annular shoulder face and anadjacent first radially inward facing surface, the second annular toothdefined by the radially outward facing undercut surface, a secondannular tooth face and a second radially inward facing surface. Thesecond annular tooth is positioned within the first annular groove withthe second annular tooth face engaging the first annular shoulder faceto define a first shoulder. The first annular tooth is positioned withinthe second annular groove with the first annular tooth face engaging thesecond annular shoulder face to define a second shoulder. The firstradially outward facing surface of the first tubular member and thesecond radially inward facing surface of the second tubular member areconfigured such that a location of primary sealing contact between thesurfaces lies outside of an axial region between the first shoulder andthe second shoulder. Likewise, the first radially inward facing surfaceof the second tubular member and the second radially outward facingsurface of the first tubular member are configured such that a locationof primary sealing contact between the surfaces lies outside of theaxial region.

In one implementation of the system of the preceding paragraph, theaxial region extends from between about 20 and about 250 thousandths ofan inch.

In one implementation of the system of either of the two precedingparagraphs, the location of primary sealing contact between the firstradially outward facing surface and the second radially inward facingsurface is external of the axial region but within at least about 1750thousandths of an inch of the axial region; and the location of primarysealing contact between the first radially inward facing surface and thesecond radially outward facing surface is external of the axial regionbut within at least about 750 thousandths of an inch of the axialregion.

In one implementation of the system of any one of the three precedingparagraphs, the location of primary sealing contact between the firstradially outward facing surface and the second radially inward facingsurface is formed by interference between one of: (i) a frustoconicalportion of the first radially outward facing surface and a frustoconicalportion of the second radially inward facing surface; (ii) afrustoconical portion of the first radially outward facing surface and acurvilinear portion of the second radially inward facing surface; (iii)a curvilinear portion of the first radially outward facing surface and afrustoconical portion of the second radially inward facing surface; or(iv) a curvilinear portion of the first radially outward facing surfaceand a curvilinear portion of the second radially inward facing surface.Likewise, the location of primary sealing contact between the firstradially inward facing surface and the second radially outward facingsurface is formed by interference between one of: (i) a frustoconicalportion of the first radially inward facing surface and a frustoconicalportion of the second radially outward facing surface; (ii) afrustoconical portion of the first radially inward facing surface and acurvilinear portion of the second radially outward facing surface; (iii)a curvilinear portion of the first radially inward facing surface and afrustoconical portion of the second radially outward facing surface; or(iv) a curvilinear portion of the first radially inward facing surfaceand a curvilinear portion of the second radially outward facing surface.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-section of one prior art center shoulder sealarrangement;

FIG. 2 is a partial cross-section of another prior art center shoulderseal arrangement;

FIG. 3 is a partial cross-section of one embodiment of a center shoulderseal;

FIG. 4 is a partial cross-section of another embodiment of a centershoulder seal; and

FIG. 5 is a partial cross-section of another embodiment of acenter-shoulder seal in which the location of primary sealing contact toopposite sides of the connection includes engaged threads to one side ofthe center-shoulder, but lacks any engaged threads to the other side ofthe center-shoulder.

DETAILED DESCRIPTION

Referring to FIG. 3, a partial cross-section of a center shoulderconnection 200 between two tubular members 202 and 204 is shown. Tubularmember 202 forms the pin portion of the connection and tubular member204 forms the box end of the connection. An axial centerline of theconnection is shown at 206, and it is recognized that a fullcross-section of the center shoulder connection would include a mirrorimage of the components on the opposite side of the axial centerline(i.e., below the centerline 206 in FIG. 3).

A seal configuration on tubular member 202 includes an annular groove208 and an annular tooth 210. The annular groove 208 is defined by aradially inward facing (i.e., facing toward the centerline 206) undercutsurface 212, an adjacent annular shoulder face 214 and an adjacentradially outward facing surface 216. The annular tooth is defined by theradially inward facing undercut surface 212, an annular tooth face 218and a radially outward facing surface 220. In the illustratedembodiment, the surface 216 includes a corner radius that transitions tothe shoulder face 214, and the surface 220 includes a corner radius thattransitions to the tooth face 218.

A seal configuration on the tubular member 204 includes an annulargroove 222 and an annular tooth 224. The annular groove 222 is definedby a radially outward facing undercut surface 226, an adjacent annularshoulder face 228 and an adjacent radially inward facing surface 230.The annular tooth 224 is defined by the radially outward facing undercutsurface 226, an annular tooth face 232 and a radially inward facingsurface 234. In the illustrated embodiment, the surface 230 includes acorner radius that transitions to the shoulder face 228, and the surface234 includes a corner radius that transitions to the tooth face 232.

FIG. 3 shows the connection in made up condition, in which the annulartooth 224 is positioned within the annular groove 208 with the annulartooth face 232 engaging the annular shoulder face 214 to define oneshoulder, which is represented by shoulder plane 236. Likewise, theannular tooth 210 is positioned within the annular groove 222 with theannular tooth face 218 engaging the annular shoulder face 228 to defineanother shoulder, which is represented by shoulder plane 238. In theillustrated embodiment the undercut surfaces 212 and 226 also engageeach other, which can act as a further sealing location, as can theengaged shoulders. At opposite axial sides of the connection, engagedthreaded sections or the tubular members are also shown schematically at260 and 262.

As illustrated, clearance may be provided between the radially outwardfacing surface 216 and the radially inward facing surface 234 invicinity of the shoulder plane 236. The location of primary sealingcontact between the radially outward facing surface 216 and the radiallyinward facing surface 234, which location is shown in FIG. 3 at 240, isspaced axially away from the shoulder plane 236 to define ametal-to-metal seal contact area 242 (represented by interference of thesurfaces shown in cross-hatch) that is axially spaced from the shoulderplane 236. As used herein the terminology “location of primary sealingcontact” between two specified surfaces means the location of maximumcontact pressure between the two surfaces. Thus, by way of example, insome embodiments surfaces 216 and 234 may make slight contact with eachother in the vicinity of the shoulder plane 236 (e.g., within an axialregion 246 between the shoulder planes 236 and 238) while, at the sametime, the location of primary sealing contact between the surfaces 216and 234 is spaced further away from the shoulder plane 236. Generally,the location of maximum contact pressure, and thus the location ofprimary sealing contact, will occur proximate the location of maximuminterference between the surfaces.

Clearance may also be provided between the radially inward facingsurface 230 and the radially outward facing surface 220 in vicinity ofthe shoulder plane 238 or, as noted above, only slight contact betweenthe surfaces may occur in the vicinity of the shoulder plane 238.Regardless, the location of primary sealing contact between the radiallyinward facing surface 230 and the radially outward facing surface 220,which location is shown in FIG. 3 at 243, is spaced axially away fromthe shoulder plane 238 to define a metal-to-metal seal contact area 244(represented by interference of the surfaces shown in cross-hatch) thatis axially spaced from the shoulder plane 238. Notably, in the case ofboth primary seal contact areas 242 and 244 of the illustratedembodiment, the location of primary sealing contact is located outsideof the axial region 246 of the connection defined between the twoshoulders planes 236 and 238.

The exact location of primary sealing contact between the surfaces(e.g., 216 and 234 or 220 and 230) can vary based upon various factors,including the necessary torque limit required in the connection, as wellas thickness and diameter of the tubular connection.

By way of example: the location of primary sealing contact 240 may beaxially spaced from the shoulder plane 236 by between about 25thousandths of an inch and about one inch; the location of primarysealing contact 243 may be axially spaced from the shoulder plane 238 bybetween about 25 thousandths of an inch and about one inch; the axialregion 246 may extend from between about 20 thousandths of an inch andabout 250 thousandths of an inch; a radial spacing between the radiallyoutward facing surface 216 and the radially outward facing surface 220in the shoulder plane 236 may be between about 40 thousandths of an inchand about 500 thousandths of an inch; and a radial spacing between theradially inward facing surface 230 and the radially inward facingsurface 234 in the shoulder plane 238 may be between about 40thousandths of an inch and about 500 thousandths of an inch.

In the illustrated embodiment, each of the surfaces 216, 220, 230 and234 are shown as curvilinear surfaces. Such curvilinear surfaces may, byway of example, when considered in two dimensions along a plane thatextends through and runs parallel to the central axis 206 of theconnection, include elliptical curves, circular curves, varying radiuscurves of any suitable type (e.g., curve radius generally between about0.5″ and about 15″ for most effective sealing), or combinations thereof,and the corresponding 3-D surface shapes produced upon rotation of anysuch curve about the central axis 206 of the connection. However, it isrecognized that the surfaces need not be entirely curvilinear or, forthat matter, curvilinear at all. For example, in one possible modifiedversion of the embodiment of FIG. 3, surfaces 220 and 234 remaincurvilinear, but surfaces 216 and 230 are made frustoconical, such thateach location of primary sealing contact 240 and 243 is made withrespect to an interference between a curvilinear surface and afrustoconical surface.

Referring to the alternative embodiment shown in FIG. 4, an embodimentof a center shoulder seal configuration 300 with axial centerline 306 inwhich the primary metal-to-metal contact seals are not formed bycurvilinear surface portions is shown. In this arrangement, the pin endon tubular member 302 includes an annular groove 308 and an annulartooth 310. The annular groove 308 is defined by a radially inward facing(i.e., facing toward the centerline 306) undercut surface 312, anadjacent annular shoulder face 314 and an adjacent radially outwardfacing surface 316. The annular tooth is defined by the radially inwardfacing undercut surface 312, an annular tooth face 318 and a radiallyoutward facing surface 320. The box end on tubular member 304 includesan annular groove 322 and an annular tooth 324. The annular groove 322is defined by a radially outward facing undercut surface 326, anadjacent annular shoulder face 328 and an adjacent radially inwardfacing surface 330. The annular tooth 324 is defined by the radiallyoutward facing undercut surface 326, an annular tooth face 332 and aradially inward facing surface 334.

Surface 316 includes cylindrical portion 316 a and frustoconical portion316 b, while surface 334 includes cylindrical portion 334 a andfrustoconical portion 334 b. Clearance may be provided between surfaceportions 316 a and 334 a, but the frustoconical portions 316 b and 334 binterfere in a manner to produce a location of primary sealing contact340 that is axially spaced from shoulder plane 336, represented byinterference contact area 342. Surface 320 includes cylindrical portion320 a and frustoconical portion 320 b, while surface 330 includescylindrical portion 330 a and frustoconical portion 330 b. Clearance maybe provided between surface portions 320 a and 330 a, but thefrustoconical portions 320 b and 330 b interfere in a manner to producea location of primary sealing contact 343 that is axially spaced fromshoulder plane 338, represented by interference contact area 344. To bemost effective, the conical angle of each frustoconical portion 316 b,334 b, 320 b, 330 b relative to the central axis 306 of the connection(e.g., represented in one instance in FIG. 4 by angle ⊖ relative to line321 that runs parallel to the central axis 306), as well as the conicalangle of other embodiments incorporating frustoconicaly surfaceportions, may be between about 1° and about 7°. Engaged threadedsections 360 and 362 on opposite axial sides of the center shoulder arealso shown. The axial locations of the seals and the radial thickness ofthe tubular members may be similar to that mentioned above with respectto the embodiment of FIG. 3.

Still other variations are possible. It is recognized that either of theprimary metal-to-metal contact seals, which are axially spaced from theshoulders, may be formed by (i) a frustoconical portion of one surfaceand a frustoconical portion of the other surface; (ii) a frustoconicalportion of the one surface and a curvilinear portion of the othersurface; (iii) a curvilinear portion of the one surface and afrustoconical portion of the other surface; or (iv) a curvilinearportion of the one surface and a curvilinear portion of the othersurface.

Generally, each of the pin part and box part may be produced using alathe process with cutting inserts profiled to produce the desiredcenter shoulder configuration on each part. By properly specifying,selecting and machining the radial location of each of the radiallyoutward facing and radially inward facing surfaces, and each point alongsuch surfaces, from the intended centerline, the locations of maximuminterference can be preselected to position the locations of primarysealing contact axially away from the shoulders of the connection.

Referring now to FIG. 5, an embodiment of a center shoulder sealconfiguration 500 with axial centerline 506 in which one side of theconnection lacks engaged threads is shown. In this arrangement, the pinend on tubular member 502 includes an annular groove 508 and an annulartooth 510. As in the previous embodiments, the annular groove 508 isdefined by a radially inward facing (i.e., facing toward the centerline506) undercut surface, an adjacent annular shoulder face 514 and anadjacent radially outward facing surface 516. The annular tooth 510 isdefined by the radially inward facing undercut surface, an annular toothface 518 and a radially outward facing surface 520. The box end ontubular member 504 includes an annular groove 522 and an annular tooth524. The annular groove 522 is defined by a radially outward facingundercut surface, an adjacent annular shoulder face 528 and an adjacentradially inward facing surface 530. The annular tooth 524 is defined bythe radially outward facing undercut surface, an annular tooth face 532and a radially inward facing surface 534.

In the illustrated embodiment, surface 516 and surface 534 areconfigured such that the location of primary sealing contact 540 isspaced further from the axial region 546 between the shoulder planes 536and 538 than the location of primary sealing contact 543 betweensurfaces 520 and 530. In this arrangement, the location of primarysealing contact 540 may be axially spaced from the shoulder plane 536 bybetween about 25 thousandths of an inch and about two inches; thelocation of primary sealing contact 543 may be axially spaced from theshoulder plane 538 by between about 25 thousandths of an inch and aboutone inch; the axial region 546 may extend from between about 20thousandths of an inch and about 250 thousandths of an inch; a radialspacing between the radially outward facing surface 516 and the radiallyoutward facing surface 520 in the shoulder plane 536 may be betweenabout 40 thousandths of an inch and about 500 thousandths of an inch;and a radial spacing between the radially inward facing surface 530 andthe radially inward facing surface 534 in the shoulder plane 538 may bebetween about 40 thousandths of an inch and about 500 thousandths of aninch. In this case the location of primary sealing contact 540 willgenerally be within 1.75 inches of the axial region 546.

Surfaces 516 and 534 include respective cylindrical surface portions516A and 534A with clearance provided. Surface portion 516A is followedby a curvilinear surface portion 516B, and surface portion 534A isfollowed by a frustoconical surface portion 534B, with location ofprimary sealing contact 540 occurring between portions 516B and 534B.Surface 530 includes a frustoconical portion 530A, followed by another,steeper frustoconical portion 530B, and surface 520 includes acurvilinear portion 520A that transitions to a cylindrical portion 520B.The location of primary sealing contact is between surface portion 530Aand surface portion 520A. It is noted that other surface variations arepossible as previously discussed. Engaged threaded sections 562 arelocated to one side of the center-shoulder, specifically the side thatis closer to the outer diameter of the connection, while the oppositeside of the connection lacks any engaged threads. Notably, on thisopposite side of connection a gap 550 may be provided between the pinnose shoulder face and the box shoulder face as shown to prevent the pinnose section from yielding due to torque, compression and expansion ofthe material at high temperatures. The faces may, however, come intocontact, such as at make-up, during compression or during materialexpansion. Also shown is a dope relief recess 560 in the surface 530 ofbox member 504 that will take-up excess thread dope as the connectionmakes up.

The configuration of FIG. 5 is particularly suited for use in connectionwith tubulars used in the geothermal markets, such as the steam assistedgravity drainage market. Although the FIG. 5 embodiment lacks anyengaged threaded section at one side of the connection, it is recognizedthat variations are possible, including implementations in which anengaged threaded section is also provided on the side of the connectionthat includes the location of primary sealing contact 540 that is spacedfurther from the axial shoulder region 546.

Thus, a method of producing tubular members with a center shoulder thatseparates metal-to-metal seals from high stress areas of the centershoulder is provided. The method involves: producing first and secondtubular members, each with a pin end and a box end, where: (a) each pinend includes: a center shoulder configuration having a first annulargroove and a first annular tooth, the first annular groove defined by aradially inward facing undercut surface, an adjacent first annularshoulder face and an adjacent first radially outward facing surface, thefirst annular tooth defined by the radially inward facing undercutsurface, a first annular tooth face and a second radially outward facingsurface, and at least a first threaded section on a larger diameter sidethe center shoulder configuration; (b) each box end includes: a centershoulder configuration having a second annular groove and a secondannular tooth, the second annular groove defined by a radially outwardfacing undercut surface, an adjacent second annular shoulder face and anadjacent first radially inward facing surface, the second annular toothdefined by the radially outward facing undercut surface, a secondannular tooth face and a second radially inward facing surface, and atleast a first threaded section on a larger diameter side of the centershoulder configuration; (c) the center shoulder configuration and firstthreaded section of the pin end of the first tubular member configuredfor mating connection with the center shoulder configuration and firstthreaded section of the box end of the second tubular member such thatupon make-up of the pin end of the first tubular member with the box endof the second tubular member: (i) the second annular tooth will bepositioned within the first annular groove with the second annular toothface engaging the first annular shoulder face to define a first shoulderand the first annular tooth will be positioned within the second annulargroove with the first annular tooth face engaging the second annularshoulder face to define a second shoulder; (ii) a location of primarysealing contact between the first radially outward facing surface of thepin end of the first tubular member and the second radially inwardfacing surface of the box end of the second tubular member will beaxially spaced apart from the first shoulder; and (iii) a location ofprimary sealing contact between the first radially inward facing surfaceof the box end of the second tubular member and the second radiallyoutward facing surface of the pin end of the first tubular member willbe axially spaced apart from the second shoulder.

Likewise, a method of connecting tubular members for use within an oilor gas well is provided and involves: (a) utilizing first and secondtubular members, each with a pin end and a box end, where: (i) each pinend includes: a center shoulder configuration having a first annulargroove and a first annular tooth, the first annular groove defined by aradially inward facing undercut surface, an adjacent first annularshoulder face and an adjacent first radially outward facing surface, thefirst annular tooth defined by the radially inward facing undercutsurface, a first annular tooth face and a second radially outward facingsurface, and at least a first threaded section on a larger diameter sideof the center shoulder configuration, and (ii) each box end includes: acenter shoulder configuration having a second annular groove and asecond annular tooth, the second annular groove defined by a radiallyoutward facing undercut surface, an adjacent second annular shoulderface and an adjacent first radially inward facing surface, the secondannular tooth defined by the radially outward facing undercut surface, asecond annular tooth face and a second radially inward facing surface,and at least a first threaded section on a larger diameter side of thecenter shoulder configuration; (b) engaging the pin end of the firsttubular member with the box end of the second tubular member; (c)producing relative rotation between the first tubular member and thesecond tubular member such that interaction of the first threadedsections of the first and second tubular members moves the first andsecond tubular members together; and (d) completing make up of the pinend of the first tubular member and the box end of the second tubularmember such that: (i) the second annular tooth is positioned within thefirst annular groove with the second annular tooth face engaging thefirst annular shoulder face to define a first shoulder and the firstannular tooth is positioned within the second annular groove with thefirst annular tooth face engaging the second annular shoulder face todefine a second shoulder; (ii) a location of primary sealing contactbetween the first radially outward facing surface of the pin end of thefirst tubular member and the second radially inward facing surface ofthe box end of the second tubular member is axially spaced apart fromthe first shoulder; and (iii) a location of primary sealing contactbetween the first radially inward facing surface of the box end of thesecond tubular member and the second radially outward facing surface ofthe pin end of the first tubular member is axially spaced apart from thesecond shoulder.

It is to be clearly understood that the above description is intended byway of illustration and example only, is not intended to be taken by wayof limitation, and that other changes and modifications are possible.

What is claimed is:
 1. A metal-to-metal sealing system connecting firstand second tubular members comprising: a metal-to-metal sealing systemconnecting first and second tubular members comprising: a first sealconfiguration on the first tubular member including a first annulargroove and a first annular tooth, the first annular groove defined by aradially inward facing undercut surface, an adjacent first annularshoulder face and an adjacent first radially outward facing surface, thefirst annular tooth defined by the radially inward facing undercutsurface, a first annular tooth face and a second radially outward facingsurface; a second seal configuration on the second tubular memberincluding a second annular groove and a second annular tooth, the secondannular groove defined by a radially outward facing undercut surface, anadjacent second annular shoulder face and an adjacent first radiallyinward facing surface, the second annular tooth defined by the radiallyoutward facing undercut surface, a second annular tooth face and asecond radially inward facing surface; wherein the second annular toothis positioned within the first annular groove with the second annulartooth face engaging the first annular shoulder face to define a firstshoulder; wherein the first annular tooth is positioned within thesecond annular groove with the first annular tooth face engaging thesecond annular shoulder face to define a second shoulder; wherein alocation of primary sealing contact between the first radially outwardfacing surface of the first tubular member and the second radiallyinward facing surface of the second tubular member is spaced axiallyaway from the first shoulder, such that there is a first axial distancebetween the first shoulder and the location of the primary sealingcontact; wherein the location of primary sealing contact between thefirst radially inward facing surface of the second tubular member andthe second radially outward facing surface of the first tubular memberis axially spaced from the second shoulder, such that there is a secondaxial distance between the second shoulder and the location of theprimary sealing contact.
 2. The system of claim 1 wherein: clearance isprovided between the first radially outward facing surface and thesecond radially inward facing surface adjacent to the first shoulder;and clearance is provided between the first radially inward facingsurface and the second radially outward facing surface adjacent to thesecond shoulder.
 3. The system of claim 1 wherein the location ofprimary sealing contact between the first radially outward facingsurface and the second radially inward facing surface is axially spacedfrom the first shoulder by a greater distance than the location ofprimary sealing contact between the first radially inward facing surfaceand the second radially outward facing surface.
 4. The system of claim 1wherein the location of primary sealing contact between the firstradially outward facing surface and the second radially inward facingsurface is axially spaced from the first shoulder by between about 25thousandths of an inch and about two inches, and the location of primarysealing contact between the first radially inward facing surface and thesecond radially outward facing surface is axially spaced from the secondshoulder by between about 25 thousandths of an inch and about one inch.5. The system of claim 1 wherein a radial spacing between the firstradially outward facing surface and the second radially outward facingsurface in a plane of the first shoulder is between about 40 and about500 thousandths of an inch, and a radial spacing between the firstradially inward facing surface and the second radially inward facingsurface in a plane of the second shoulder is between about 40 and about500 thousandths of an inch.
 6. The system of claim 1 wherein theradially inward facing undercut surface engages the radially outwardfacing undercut surface.
 7. The system of claim 1 wherein: the locationof primary sealing contact between the first radially outward facingsurface and the second radially inward facing surface is formed byinterference between one of: (i) a frustoconical portion of the firstradially outward facing surface and a frustoconical portion of thesecond radially inward facing surface; (ii) a frustoconical portion ofthe first radially outward facing surface and a curvilinear portion ofthe second radially inward facing surface; (iii) a curvilinear portionof the first radially outward facing surface and a frustoconical portionof the second radially inward facing surface; or (iv) a curvilinearportion of the first radially outward facing surface and a curvilinearportion of the second radially inward facing surface; the location ofprimary sealing contact between the first radially inward facing surfaceand the second radially outward facing surface is formed by interferencebetween one of: (i) a frustoconical portion of the first radially inwardfacing surface and a frustoconical portion of the second radiallyoutward facing surface; (ii) a frustoconical portion of the firstradially inward facing surface and a curvilinear portion of the secondradially outward facing surface; (iii) a curvilinear portion of thefirst radially inward facing surface and a frustoconical portion of thesecond radially outward facing surface; or (iv) a curvilinear portion ofthe first radially inward facing surface and a curvilinear portion ofthe second radially outward facing surface.
 8. The system of claim 1wherein the first radially outward facing surface of the first tubularmember and the second radially inward facing surface of the secondtubular member are configured such that the location of primary sealingcontact between the surfaces lies outside of an axial region between thefirst shoulder and the second shoulder and wherein the first radiallyinward facing surface of the second tubular member and the secondradially outward facing surface of the first tubular member areconfigured such that the location of primary sealing contact between thesurfaces lies outside of the axial region.
 9. The system of claim 8wherein the axial region extends from between about 20 and about 250thousandths of an inch.
 10. A metal-to-metal sealing system connectingfirst and second tubular members comprising: a first seal configurationon the first tubular member including a first annular groove and a firstannular tooth, the first annular groove defined by a radially inwardfacing undercut surface, an adjacent first annular shoulder face and anadjacent first radially outward facing surface, the first annular toothdefined by the radially inward facing undercut surface, a first annulartooth face and a second radially outward facing surface; a second sealconfiguration on the second tubular member including a second annulargroove and a second annular tooth, the second annular groove defined bya radially outward facing undercut surface, an adjacent second annularshoulder face and an adjacent first radially inward facing surface, thesecond annular tooth defined by the radially outward facing undercutsurface, a second annular tooth face and a second radially inward facingsurface; wherein the second annular tooth is positioned within the firstannular groove with the second annular tooth face engaging the firstannular shoulder face to define a first shoulder; wherein the firstannular tooth is positioned within the second annular groove with thefirst annular tooth face engaging the second annular shoulder face todefine a second shoulder; wherein the first radially outward facingsurface of the first tubular member and the second radially inwardfacing surface of the second tubular member are configured such that thelocation of primary sealing contact between the surfaces lies outside ofan axial region between the first shoulder and the second shoulder, suchthat there is a first axial distance between the first shoulder and thelocation of the primary sealing contact; wherein the first radiallyinward facing surface of the second tubular member and the secondradially outward facing surface of the first tubular member areconfigured such that a location of primary sealing contact between thesurfaces lies outside of the axial region, such that there is a secondaxial distance between the second shoulder and the location of theprimary sealing contact.
 11. The system of claim 10 wherein the axialregion extends from between about 20 and about 250 thousandths of aninch.
 12. The system of claim 10 wherein: the location of primarysealing contact between the first radially outward facing surface andthe second radially inward facing surface is external of the axialregion but within at least about 1750 thousandths of an inch of theaxial region; wherein the location of primary sealing contact betweenthe first radially inward facing surface and the second radially outwardfacing surface is external of the axial region but within at least about750 thousandths of an inch of the axial region.
 13. The system of claim10 wherein: the location of primary sealing contact between the firstradially outward facing surface and the second radially inward facingsurface is formed by interference between one of: (i) a frustoconicalportion of the first radially outward facing surface and a frustoconicalportion of the second radially inward facing surface; (ii) afrustoconical portion of the first radially outward facing surface and acurvilinear portion of the second radially inward facing surface; (iii)a curvilinear portion of the first radially outward facing surface and afrustoconical portion of the second radially inward facing surface; or(iv) a curvilinear portion of the first radially outward facing surfaceand a curvilinear portion of the second radially inward facing surface;the location of primary sealing contact between the first radiallyinward facing surface and the second radially outward facing surface isformed by interference between one of: (i) a frustoconical portion ofthe first radially inward facing surface and a frustoconical portion ofthe second radially outward facing surface; (ii) a frustoconical portionof the first radially inward facing surface and a curvilinear portion ofthe second radially outward facing surface; (iii) a curvilinear portionof the first radially inward facing surface and a frustoconical portionof the second radially outward facing surface; or (iv) a curvilinearportion of the first radially inward facing surface and a curvilinearportion of the second radially outward facing surface.
 14. A method ofproducing tubular members with a center shoulder that separatesmetal-to-metal seals from high stress areas of the center shoulder:producing first and second tubular members, each with a pin end and abox end, where: each pin end includes: a center shoulder configurationhaving a first annular groove and a first annular tooth, the firstannular groove defined by a radially inward facing undercut surface, anadjacent first annular shoulder face and an adjacent first radiallyoutward facing surface, the first annular tooth defined by the radiallyinward facing undercut surface, a first annular tooth face and a secondradially outward facing surface, and at least a first threaded sectionon a side of the center shoulder configuration; each box end includes: acenter shoulder configuration having a second annular groove and asecond annular tooth, the second annular groove defined by a radiallyoutward facing undercut surface, an adjacent second annular shoulderface and an adjacent first radially inward facing surface, the secondannular tooth defined by the radially outward facing undercut surface, asecond annular tooth face and a second radially inward facing surface,and at least a first threaded section on a side of the center shoulderconfiguration; the center shoulder configuration and first threadedsection of the pin end of the first tubular member configured for matingconnection with the center shoulder configuration and first threadedsection of the box end of the second tubular member and sized such thatupon make-up of the pin end of the first tubular member with the box endof the second tubular member: the second annular tooth will bepositioned within the first annular groove with the-second annular toothface engaging the first annular shoulder face to define a first shoulderand the first annular tooth will be positioned within the second annulargroove with the first annular tooth face engaging the second annularshoulder face to define a second shoulder; the location of primarysealing contact between the first radially outward facing surface of thepin end of the first tubular member and the second radially inwardfacing surface of the box end of the second tubular member will beaxially spaced apart from the first shoulder, such that there is a firstaxial distance between the first shoulder and the location of theprimary sealing contact; and the location of primary sealing contactbetween the first radially inward facing surface of the box end of thesecond tubular member and the second radially outward facing surface ofthe pin end of the first tubular member will be axially spaced apartfrom the second shoulder, such that there is a second axial distancebetween the second shoulder and the location of the primary sealingcontact.
 15. The method of claim 14 wherein: clearance is providedbetween the first radially outward facing surface and the secondradially inward facing surface adjacent to the first shoulder; andclearance is provided between the first radially inward facing surfaceand the second radially outward facing surface adjacent to the secondshoulder.
 16. The method of claim 14 wherein the location of primarysealing contact between the first radially outward facing surface andthe second radially inward facing surface is axially spaced from thefirst shoulder by a greater distance than the location of primarysealing contact between the first radially inward facing surface and thesecond radially outward facing surface.
 17. The method of claim 14wherein the location of primary sealing contact between the firstradially outward facing surface and the second radially inward facingsurface is axially spaced from the first shoulder by between about 25thousandths of an inch and about two inches, and the location of primarysealing contact between the first radially inward facing surface and thesecond radially outward facing surface is axially spaced from the secondshoulder by between about 25 thousandths of an inch and about one inch.18. The method of claim 14 wherein a radial spacing between the firstradially outward facing surface and the second radially outward facingsurface in a plane of the first shoulder is between about 40 and about500 thousandths of an inch, and a radial spacing between the firstradially inward facing surface and the second radially inward facingsurface in a plane of the second shoulder is between about 40 and about500 thousandths of an inch.
 19. The method of claim 14 wherein theradially inward facing undercut surface engages the radially outwardfacing undercut surface.
 20. The method of claim 14 wherein: thelocation of primary sealing contact between the first radially outwardfacing surface and the second radially inward facing surface is formedby interference between one of: (i) a frustoconical portion of the firstradially outward facing surface and a frustoconical portion of thesecond radially inward facing surface; (ii) a frustoconical portion ofthe first radially outward facing surface and a curvilinear portion ofthe second radially inward facing surface; (iii) a curvilinear portionof the first radially outward facing surface and a frustoconical portionof the second radially inward facing surface; or (iv) a curvilinearportion of the first radially outward facing surface and a curvilinearportion of the second radially inward facing surface; the location ofprimary sealing contact between the first radially inward facing surfaceand the second radially outward facing surface is formed by interferencebetween one of: (i) a frustoconical portion of the first radially inwardfacing surface and a frustoconical portion of the second radiallyoutward facing surface; (ii) a frustoconical portion of the firstradially inward facing surface and a curvilinear portion of the secondradially outward facing surface; (iii) a curvilinear portion of thefirst radially inward facing surface and a frustoconical portion of thesecond radially outward facing surface; or (iv) a curvilinear portion ofthe first radially inward facing surface and a curvilinear portion ofthe second radially outward facing surface.
 21. The method of claim 14wherein the first radially outward facing surface of the first tubularmember and the second radially inward facing surface of the secondtubular member are configured such that the location of primary sealingcontact between the surfaces lies outside of an axial region between thefirst shoulder and the second shoulder and wherein the first radiallyinward facing surface of the second tubular member and the secondradially outward facing surface of the first tubular member areconfigured such that the location of primary sealing contact between thesurfaces lies outside of the axial region.
 22. The method of claim 21wherein the axial region extends from between about 20 and about 250thousandths of an inch.
 23. A method of connecting tubular members,comprising: (a) utilizing first and second tubular members, each with apin end and a box end, where: each pin end includes: a center shoulderconfiguration having a first annular groove and a first annular tooth,the first annular groove defined by a radially inward facing undercutsurface, an adjacent first annular shoulder face and an adjacent firstradially outward facing surface, the first annular tooth defined by theradially inward facing undercut surface, a first annular tooth face anda second radially outward facing surface, and at least a first threadedsection on a side of the center shoulder configuration, and each box endincludes: a center shoulder configuration, having a second annulargroove and a second annular tooth, the second annular groove defined bya radially outward facing undercut surface, an adjacent second annularshoulder face and an adjacent first radially inward facing surface, thesecond annular tooth defined by the radially outward facing undercutsurface, a second annular tooth face and a second radially inward facingsurface, and at least a first threaded section on a side of the centershoulder configuration; (b) engaging the pin end of the first tubularmember with the box end of the second tubular member; (c) producingrelative rotation between the first tubular member and the secondtubular member such that interaction of at least a first threadedsection of each of the the first and second tubular members moves thefirst and second tubular members together; (d) completing make-up of thepin end of the first tubular member and the box end of the secondtubular member such that: the second annular tooth is positioned withinthe first annular groove with the second annular tooth face engaging thefirst annular shoulder face to define a first shoulder and the firstannular tooth is positioned within the second annular groove with thefirst annular tooth face engaging the second annular shoulder face todefine a second shoulder; the location of primary sealing contactbetween the first radially outward facing surface of the pin end of thefirst tubular member and the second radially inward facing surface ofthe box end of the second tubular member is axially spaced apart fromthe first shoulder, such that there is a first axial distance betweenthe first shoulder and the location of the primary sealing contact; andthe location of primary sealing contact between the first radiallyinward facing surface of the box end of the second tubular member andthe second radially outward facing surface of the pin end of the firsttubular member is axially spaced apart from the second shoulder, suchthat there is a second axial distance between the second shoulder andthe location of the primary sealing contact.